This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This is a Phase III, randomized, multi-center trial designed to compare the effect of beta-blocker therapy to that of angiotensin receptor blocker therapy on rate of change in aortic growth and progression of aortic regurgitation in individuals with Marfan Syndrome. Patients are followed for three years after randomization.